The urea enzyme kinetic assay, commonly used in the clinic to measure urea nitrogen, is a method to determine whether the urea nitrogen in the body is normal or not, so as to assess the function of the kidneys. The urea enzyme kinetic assay, which is used to determine the amount of urea nitrogen in the body after blood is drawn to assess whether kidney function is abnormal, is easily affected by food and other factors, so blood should be drawn on an empty stomach. Physiological conditions such as eating a large amount of protein, strenuous exercise, etc. will cause an increase in urea nitrogen. Pathologic conditions such as glomerulonephritis, acute and chronic renal failure, massive dehydration, and severe infections can cause elevated urea nitrogen. Low urea nitrogen can be seen in inadequate protein intake, hepatic failure, etc. Therefore, for abnormal urea nitrogen, we should consult a doctor in time, clarify the cause of the disease, and then follow the doctor’s instructions to avoid delaying the condition.